A quantitative study of the aggregation behaviour of the cationic cyanine dye pinacyanol chloride in aqueous solution and in the presence of various organic matrices (anionic alginates, anionic Aerosol-OT and g-cyclodextrin) is presented based on UV/Visible absorption and Circular Dichroism (CD) spectroscopy. The spectral data have been analysed using derivative spectra and a program (PeakFit) to model the mixtures of different absorbing species with strongly overlapping absorption bands. The structures of the aggregates have been analysed and discussed in terms of qualitative (H- vs. J-type aggregation) and quantitative arguments based on a program (OSCI) for the calculation of oscillator and rotatory strengths assuming an exciton-like delocalisation of molecular excitations through the entire aggregate. Models for the various complexes of the dye in the presence of various organic matrices have been proposed

Reactions of photoexcited 1,2-dicarbonyl compounds with chirally labelled and unlabelled captodative alkenes have been investigated, with special emphasis on their diastereoselection in cycloadditions. Irradiation of methyl phenylglyoxylate in presence of unlabelled alkenes yields to the corresponding rel-(2R, 3R)-head-to-head-oxetanes. Using the chirally labelled (S)-(methoxymethylpiperidinyl)propenenitrile gives rise to two oxetanes, one of which was isolated and identified as (2R, 3R)-head-to-head-oxetane by X-ray cristallography. Additionally, the photoreduction product meso-dimethyl-2,3-diphenyltartrate of the ester was formed in all reactions. The photoreactions of benziles with chirally labelled c,d-alkenes give rise to oxetanes in low yields, in these cases the products of Norrish type I reactions become competitive.

The thesis describes the investigation of high-resolution MQ MAS NMR in rigid spin-1/2 systems. Formerly, MQC techniques were mainly applied to systems of small molecules, the newly developed MQC technique in this thesis, the 1H-MQC-filtered-MAS-NMR method, can be well applied to study the heterogeneity of inorganic and organic materials, such as silica gel, homopolymers, copolymers and their blends. In this thesis two multiple-pulse sequences were adopted: the three-pulse and the time-reversible eight-pulse sequence. The former has the advantage that the cycle time, i.e. the excitation time can be adjusted to arbitrary values, therefore it can be used to generate 1H MQC in coupled spin-1/2 systems for a wide range of dipolar interactions, especially to pump 1H MQC from a rigid system, such as the crystalline phase of polymers. But it has disadvantages: it is sensitive to chemical shifts and resonance offsets, and has low efficiency in exciting higher order coherences. The latter has higher efficiency in exciing higher order coherences and is not sensitive to chemical shifts and resonance offsets, but it has a long cycle time, so it is only effective when the dipolar interactions are not strong such as in the amorphous phase of polymers

Im Rahmen dieser Arbeit wurden die Metallzentren der Cytochrom-c-Oxidasen (CCO) aus Thermus thermophilus (T.t.), aus Paracoccus denitrificans (P.d.) und dreier mit gentechnischen Methoden erzeugten Proteine (M227I, C216S, SU II) mit Hilfe der EXAFS-Spektroskopie untersucht. Die EXAFS-Messungen an der löslichen Domäne der Untereinheit II der CCO aus P.d. exprimiert in E. coli (SU II) ermöglichten erstmals die Untersuchung eines CuA-Zentrums mit EXAFS ohne die Überlagerung durch Signale von CuB. Das CuA-Zentrum ist ein zweikerniges Zentrum mit sehr kurzem Cu-Cu-Abstand dessen Kupfer-Atome von zwei (mü)2-Schwefel-Liganden verbrückt werden. Terminal an die beiden Cu-Atome koordiniert jeweils ein Histidin. Es kann nicht ausgeschlossen werden, daß die in verschiedenen Arbeiten als schwach koordinierend diskutierten Methionin- und Glutamat-Backbone-Liganden maskiert und damit nicht zu detektieren sind. Somit ist eine CuA-Zentrum. Am CuB koordinieren drei Histidinliganden. Der mittlere Fe-Cu-Abstand im Fea3/CuB-Zentrum beträgt 3,99 Å. Die beiden Eisenatome des Enzyms sind durch je einen Porphyrin-Ring koordiniert. Das Feb-Zentrum vervollständigt seine Koordination durch zwei axial zum Ring gebundene Histidin-Reste, das Fea3 durch einen axial gebundenen Histidin-Rest. Der Vergleich der EXAFS-Messungen an der CCO aus P.d. mit denen für die CCO aus T.t. zeigt, daß die Metallzentren der beiden Enzyme bis auf Details identisch sind. Das Kupfer-EXAFS der Mutante M227I der CCO aus P.d. zeigt eine Erhöhung der mittleren Koordinationszahl der Kupfer-Atome im mutierten CuA-Zentrum auf vier. Die daraus resultierende strukturelle Änderung bedingt eine Spin-Lokalisation im nativ Spin-delokalisierten Zentrum. Offensichtlich ist das in CCO hochkonservierte Methionin 227 erforderlich, um die einzigartige geometrische und elektronische Struktur des CuA-Zentrums zu stabilisieren. Die spektroskopischen Untersuchungen an der Mutante C216S der CCO aus P.d. zeigen statt des CuA-Zentrums ein einkerniges Kupfer-Zentrum an der Bindungsstelle des dem konservierten Methionin 227 zugewandten Kupferatoms des CuA-Zentrums. Das Zentrum wird durch ein Histidin, ein Cystein, ein Methionin und einen weiteren Liganden (S/Cl) tetraedrisch koordiniert. Es wird deutlich, daß das im CuA verbrückend koordinierende Cystein 216 essentiell zur Bildung eines homodinuklearen Zentrums ist. Ausserdem wurde eine optimierte Meßstrategie entworfen, mit der die zur Verfügung stehende Meßzeit zugunsten der kritischen Bereiche des Spektrums teilweise umverteilt wird. Es wurde eine neuartige Methode zur quantitativen Bestimmung der statistischen Qualität von EXAFS-Spektren entwickelt. Mit Hilfe dieser Methode konnte ein neuartiges dynamisch-adaptives Verfahren zur Glättung von Spektren entwickelt und programmiert werden. Es wurden zusätzlich Erweiterungen zur Standardsoftware Cerius2 entwickelt. Die Erweiterungen ergänzen die Funktion und die Oberfläche des Programms.

This thesis describes the measurement of xenon diffusion coefficients in porous media via Pulsed Field Gradient (PFG) NMR spectroscopy. The thesis includes the characterization of a phase seperated polymer blend (PP/EPDM) in comparison to the pure components, the characterization of a number of commercially available semi-crystalline polymers and the characterization of a new microporous solid catalyst (silconimidonitride) with three different pore sizes by the diffusional behaviour of xenon in these materials. In addition to that a new theory is described which correlates the chemical shift of 129Xe NMR adsorption resonances with the corresponding xenon diffusion coefficients.

Reactions of photoexcited coumarins and their thia analogues with captodative alkenes have been investigated, with special emphasis on the nature of the excited states and the specific influence of the substrates on regio- and stereoselectivity of the observed [2+2]-photocycloadditions. Aside of two coumarin thiones all coumarins investigated regioselectively add captodative alkenes at the pyranone moeity giving rise to head-to-tail [2+2]-photocycloadducts with donor-endo adducts as prevailing isomers. The observed regio- and stereoselectivities can be best explained if a 1,4-biradical is assumed as intermediate in the photocycloaddition.

In the theoretical part of this work it is shown that the Lamm´s Differential Equation for polymer solutions can be extended to swollen polymer networks, if the phenomenological equations and the equation for the chemical potential of the polymer component in the network are taken into account. All differences for a transition from a polymer solution to a swollen polymer network can be assigned a "Elastically active coefficient E", which describes a deformation velocity with the same unit as the diffusion coefficient. In the practical part of this thesis some new improvements/developments regarding the Schlieren optical system are introduced and discussed. In the part "Results and Discussion" the results of the centrifugal measurements of gelatine gels are presented and discussed. The following evaluation of the centrifugal runs of polyacrylat gels (chemical networks) and the comparison with the results of the gelatine gels (physical networks) shows clearly that the new theory is suitable to describe the move ment of the polymer component in the network in a centrifugal field quantitatively as well as qualitatively.

Host and guest compounds self-assemble to supramolecular complexes. Noncovalent bonding donor-acceptor-interactions of supramolecular complexes like that of J. F. Stoddart et al. can be weakened by redox reactions, but the complexes desintegrate. Here, it is described the reversed way. The initial reaction mixture contains a host and a potential guest compound not interacting with each other. The potential guest compound will be transferred in a real guest compound by electrochemical reduction and the supramolecular complexation is induced. Tetracationic, electronwithdrawing cyclophanes with two redoxactive units of 4,4-bipyridindiium respectively 2,7-diazapyrendiium act as host compounds, electronwithdrawing quinones as potential guest compounds. The host and guest compounds and their interaction in complex are characterized and studied by cyclic voltammetry and spectroelectrochemistry. It can be demonstrated that the reduction potentials are shifted, that the cyclophane and the guest compound form an inclusion complex and that the inclusion complexes are low soluble, exclusion complexes well soluble.

In inductively coupled plasma spectrometry, signal suppression by acids has been recognized for a long time. It is always explained as the physical effects on the sampling processes, plasma conditions, and aerosol properties. In some cases, signal suppression apparently relates to the chemical properties of element. However, there was no publication discussed this phenomenon. In this work, it has been proven that mercury signal suppression depends on the plasma properties and nitric acid concentration. It relates to the atomization yield of mercury compounds, which is governed by the red-ox equilibrium in the central channel of plasma. Mercury complex formation equilibrium has been proven to exert in the heated droplets in plasma. The equilibrium state is governed by the complex formation with ammonium nitrate, the complex dissociation by nitric acid, and the heat obtained from plasma. Mercury halogen complex is not sensitive to the changes in acidity. Therefore, it is able to keep mercury free from nitric acid interferences and unify mercury atomization in the central channel of plasma. Similar to mercury, the uncertain signal and memory effect of platinum group elements and gold mainly arises from the chemical interference on the atomization efficiency. It not only depends on nitric acid concentration, but also on the standard reduction potential (Eo) of precious metal species in solution. Chemical interference on the spectrometric signals is governed by the robustness of the plasma, the capabilities to ingest aerosol and to protect foreign disturbance. The robustness of plasma is not equal to the excitation conditions. It has been observed that nitric acid has no significant interferences on mercury signal intensity of MIP-OES. When wet aerosol enters into the resonant cavity, it is completely desolvated in the powerful electromagnetic field. Liquid phase instantly disappears from the plasma observation zone. No doubt, the chemical equilibrium does not exist. In conclusion, chemical reactions exist in the plasma and interference the spectrometric signal. The best way to overcome the chemical matrix interferences in the plasma source spectrometry is to realize the controllable atomization.

Nanocapsules are generally considered as spherical, hollow structures. Important potential applications are pharmaceutically related such as drug targeting and controlled release. Typically, the capsules consist of a polymeric wall, filled with an oil which can dissolve lipophilic agents. To enable a stable aqueous dispersion, the capsule surface is covered by an amphiphilic surfactant. Nanocapsule-dispersions were investigated by means of solid-state nmr. Cross polarization experiments revealed the morphology of the polymeric wall. Further, the spin-lattice relaxation times for the proton magnetization in the rotating frame were studied under direct excitation as well as under cross polarization conditions. Based on the results, a special mechanism of cross polarization is proposed, initiated by a temporary adsorption of mobile oil- and surfactant-molecules to the more rigid capsule surface. - Nanokapseln sind sphärische, hohle Objekte, die in der Medizin als gewebespzifische Wirkstoff-Träger-Systeme eingesetzt werden sollen. Vereinfacht bestehen die Kapseln aus einem Öltropfen, der von einem Polymergerüst umgeben ist. In die innere Ölphase können lipophile Wirkstoffe eingeschlossen werden. Die Nanokapselwand ist mit einer Tensidschicht umgeben, die stabilisierend wirkt und ermöglicht, dass die Kapseln in einer wässerigen Phase dispergiert werden können. Als analytische Methode wurde die Festkörper-NMR-Spektroskopie gewählt. Die Morphologie der Polymerwand wurde mit Kreuzpolarisationsexperimenten aufgeklärt. Zusätzlich wurden die Relaxationszeiten im rotierenden Koordinatensystem der Protonen unter Direktanregungs- und Kreuzpolarisationsbedingungen untersucht. Die Ergebnisse dieser Untersuchungen konnten mit einer temporären Adsorption der Öl- und Tensidmoleküle an der Nanokapseloberfläche interpretiert werden.